1. Technical Field
The present invention relates to a manufacturing method of a quartz crystal resonator for manufacturing an AT cut quartz crystal resonator having a convex sectional shape by processing a crystal chip, an apparatus for the method, and a quartz crystal resonator manufactured by this manufacturing method or this manufacturing apparatus.
2. Related Art
In a conventional method for manufacturing a piezoelectric resonator, blasting is applied to either or both of an AT cut quartz crystal wafer by spraying fine abrasives from a nozzle with a small bore onto desired narrow ranges at both sides along visible outlines of a piezoelectric element piece, thereby manufacturing a piezoelectric element piece having a convex sectional shape (for example, refer to Japanese Unexamined Patent Publication No. 2003-37463 (page 1, [0019] to [0024], FIGS. 1 to 4)). Hereinafter this technique is referred to as a first conventional example.
A conventional manufacturing device of a piezoelectric element plate is a device for manufacturing a piezoelectric element plate having at least one surface with a convex-shaped portion, the manufacturing device comprising: a base for holding a large element plate having a plurality of element plate chips that have still not been separated; and a plurality of polishing members descending and ascending and rotating on or above the top surface of the large element plate held on the base; wherein the plurality of polishing members, which are cylindrical, are provided to correspond one-to-one to element plate chips, each polishing member having a concave polishing surface at its bottom. Each polishing member touches the top surface of each element plate chip and polishes a surface of the element plate chip while rotating and descending, thereby processing the top surfaces of element plate chips to be convex-shaped (for example, refer to Japanese Unexamined Patent Publication No. H11-298278 (page 1, claim 1, [0005] to [0007], FIGS. 1 and 2)). Hereinafter this technique is referred to as a second conventional example.
A conventional method for manufacturing a quartz crystal resonator forms thick and large electrodes on the two main surfaces of a AT cut crystal element plate, which is a flat plate, and then sharpens these electrodes by laser trimming, and therefore creates a stair-like and angled structure in which an area becomes concentrically or spirally narrower as heading the top, thereby forming the whole shape of the quartz crystal resonator to be convex (for example, refer to Japanese Unexamined Patent Publication No. H10-308645 (page 1, claim 4, [0005] and [0008], FIG. 4)). Hereinafter this technique is referred to as a third conventional example.
A conventional method for manufacturing a piezoelectric vibration element comprises a cutting process of cutting down a piezoelectric crystal at an arbitrary angle, a piezoelectric device element formation process of processing the cut piezoelectric crystal into a piezoelectric device element of an arbitrary size, convex lens shape processing process of processing at least after the cutting process the entire or part of one main surface to be in a convex lens shape, a protective film formation process of forming a protective film on at least a main surface of a convex lens shape, and etching process of processing the element, except the protective film formation portion where the protective film is formed (for example, refer to Japanese Unexamined Patent Publication No. 2003-60481 (page 1, claim 9, [0026] to [0029], FIG. 7)). Hereinafter this technique is referred to as a fourth conventional example.
In a conventional method for manufacturing a quartz crystal resonator, a laser beam is applied to the polished crystal wafer, thereby processing this crystal wafer such that its thickness is thin and uniform. Oscillation frequency is measured for each minute portion of the entire surface of the processed crystal wafer using a large number of measuring microelectrodes located in a grid pattern on a glass substrate. Based on the measured results, a laser beam is applied to the portions of the crystal wafer that are thicker than a predetermined thickness to modify the thickness of the portions. Then, after forming a large number of electrodes in a predetermined size on the entire surface of the crystal wafer at predetermined intervals, quartz crystal resonators, which are chips with electrodes, are manufactured by dicing each electrode portion of the crystal wafer (for example, refer to Japanese Unexamined Patent Publication No. 2000-286657 (claim 1, [0005] and [0010] to [0013], FIGS. 1, 2, 4 and 5)). Hereinafter this technique is referred to as a fifth conventional example.
In a conventional method for processing a piezoelectric element, a ring-shaped, quadrangular, or other shaped groove or step is formed on the top surface of a first auxiliary tool, and a second auxiliary tool, which is cylindrical or other shaped and is slightly higher than the groove or step, is fitted to the groove or step. A disk shaped or other shaped piezoelectric element to be polished, which has a height equal to or slightly lower or higher than that of the portion of the second auxiliary tool that is protruding from the top surface of the first auxiliary tool, is installed. An extremely thin workpiece is polished using two wrapping plates, the upper wrapping plate on the top surface of the piezoelectric element to be polished and the lower wrapping plate under the first auxiliary tool (for example, refer to Japanese Unexamined Patent Publication No. 2000-317782 (claim 1, [0005] and [0009] to [0013], FIGS. 1 and 2)). Hereinafter this technique is referred to as a sixth conventional example.
As a conventional method for processing a quartz crystal resonator, there is an example of mixing a crystal chip with abrasives, putting the mixture into a container, which is referred to as a barrel, rotating the container, and bringing the crystal chip inside the container into contact with abrasives and the wall surface of the container by the rotational movement, thereby convex processing the crystal chip. Hereafter this technique is referred to as a seventh conventional example.
The above described first conventional example has problems that controlling its shape becomes difficult as an AT cut quartz crystal resonator is miniaturized and roughness of a surface of an AT cut quartz crystal wafer and a degenerated layer occur due to the use of blasting, which sprays fine abrasives to break an AT cut quartz crystal wafer. The above described second conventional example also has, in addition to the same problems as mentioned for the first conventional example, a problem that the example can be applied just to the disk shaped AT cut quartz crystal resonators and therefore the versatility is low. In the above described third conventional example, there are problems that the formation of an electrode having a stair-like and angled structure takes a large number of man-hours, causing a rise in cost, and the whole electrode becomes thick, increasing the load in driving an AT cut quartz crystal resonator.
The above described fourth conventional example has a problem that a sufficient performance cannot be obtained because a convex shape can be formed just on one side of the crystal chip. In the above described fifth and sixth conventional examples, there is a problem that special equipment and tools are required for processing an AT cut quartz crystal wafer, thereby causing a rise in cost of an AT cut quartz crystal resonator. The above described seventh conventional example has problems of an extremely long processing time (it may be counted by the hundreds), inferior controllability of shape, and the difficulty in processing a small quartz crystal piece.
The present invention aims to solve the above described problems and is intended to obtain a method for manufacturing a quartz crystal resonator, an apparatus for the method, and a quartz crystal resonator manufactured by the method or the apparatus, whereby control of the shape of a quartz crystal resonator is easy even if the quartz crystal resonator is miniaturized, the shape and the performance of a processed quartz crystal resonator are satisfactory, quartz crystal resonators of various shapes can be formed, a quartz crystal resonator can be formed at low cost with a small number of man-hours, a load in driving a quartz crystal resonator is small, and versatile equipment and tools can be used.